The Limitations of the WSR-88D Radar Network for Quantitative Precipitation Measurement over the Coastal Western United States

Abstract

An objective assessment of the WSR-88D radar coverage for detection and quantitative measurement of precipitation over the U.S. west coast is presented. As a result of significant terrain blockage, shallow precipitation, and low freezing levels, only one-fourth to one-third of the land surface in the region has sufficient radar coverage for precipitation estimation. Furthermore, it was found that the radar coverage is not representative of the precipitation distribution, with poor radar coverage in the regions where the most rainfall occurs. Radar-derived storm-total precipitation estimates from the Portland, Oregon, radar for the catastrophic flood of February 1996 illustrate the limitations of the network, showing that the radar estimates in the heaviest precipitation regions to be less than 50% of the rain gauge values. A comparison of the WSR-88D coverage with the regional rain gauge network reveals that rain gauges will continue to be the major source of precipitation data over most of the region.